The present invention relates to steering devices such as may be used with catheters, cannulae, guidewires and the like. More particularly, the present invention relates to catheters and guidewires that are steerable through body lumen or cavities and positionable within or aimable at obstructions, organs, or tissue within the body from a position external to the body.
Medical catheters generally comprise elongate tubelike members which may be inserted into the body, either percutaneously or via a body orifice, for any of a wide variety of diagnostic and therapeutic purposes. Such medical applications frequently require use of a catheter having the ability to negotiate twists and turns, particularly with regard to certain cardiovascular applications.
One such application, Percutaneous Transluminal Coronary Angioplasty (balloon angioplasty), requires manipulation of a catheter from a position outside the patient's body through extended portions of the patient's arterial system to the stenotic site for the purpose of alleviating the obstruction by inflating a balloon. This particular procedure has been performed with increasing frequency over the past years in preference to open heart bypass surgery, when possible.
In a typical angioplasty procedure, a guidewire is transluminally inserted into the brachial or the femoral artery, to be positioned within the stenotic region and followed by a balloon catheter. The cardiologist usually prebends the distal tip of the guidewire before insertion and then rotates (or torques) the wire once it has reached a branch artery to enable the guidewire to enter the branch. If the angle of the bend has to be adjusted, the guidewire must be removed, re-bent and reinserted, sometimes several times. Particular difficulty is encountered with prebending where an artery branches at one angle, and then sub-branches at a different angle. This procedure is attended by the risk of significant trauma to the arterial lining, and, in many cases, the obstruction cannot be reached at all with the guidewire and catheter.
Coronary arteries are tortuous, have many sub-branches and often the obstruction is either located where the diameter of the artery is small or, by its very presence, the obstruction leaves only a very small opening through which a guidewire and/or catheter can be passed. Consequently, the cardiologist often finds it very difficult to maneuver the guidewire or catheter, which are typically several feet long, from the proximal end.
Steering the prebended guidewire is further complicated by the fact that branches project at all different radial angles, thus necessitating rotation of the guidewire to the appropriate degree to enter the desired arterial branch. However, rotation of the distal end of the wire typically lags behind rotation of the proximal, control end, so that precise rotational control is not possible. Also, friction in the arteries can cause the distal end to rotate in a jerky fashion which can traumatize the vascular intima.
In another application, Transluminal Laser Catheter Angioplasty (laser angioplasty), the delivery of laser energy from an external source to an intraluminal site to remove plaque or thrombus obstructions in vessels is accomplished by providing a waveguide such as a fiber optic bundle within a catheter. The nature of laser angioplasty requires an even greater ability to precisely manipulate the catheter, to control and aim the laser light at the specific plaques or thrombi to be removed.
A variety of attempts have been made in the past to provide catheters which are steerable from the proximal end to enable the catheter to be aimed or advanced through nonlinear body cavities. For example, U.S. Pat. No. 4,723,936 to Buchbinder, et al. discloses a balloon catheter, which is said to be steerable from the proximal end. The catheter is provided with a deflection wire going along the entire length of the catheter, which may be axially displaced to cause deflection at the distal end. However, the tip of the catheter can be bent in one direction only, and the entire catheter must be rotated or torqued to be guided. In addition, the design requires a relatively large diameter deflection wire, which precludes extremely thin diameter catheters, such as those preferred for use for laser or balloon angioplasty applications.
U.S. Pat. No. 3,470,876 to Barchilon discloses a catheter device having a central lumen extending therethrough, and four tensioning cords extending along an inner wall of the catheter. The '876 patent specifically recites that catheters may be produced in accordance with the Barchilon design having diameters of 0.125 to 2 inches, and are suited for applications such as within the duodenal bulb or ascending colon. These diameters are unsuited for use as a guidewire in coronary angioplasty, which typically requires diameters in the area of as small as from about 0.014 to 0.018 inches.
In the context of coronary angioplasty applications, the prior art generally suffers from disadvantages such as limited steerability and excessive external diameters. Limited catheter tip steerability results in greater time spent in the body and significantly elevated risk of trauma both to the vascular intima and to the patient in general. Multiple insertions of guidewires or catheters may lead to thrombosis, as a result of coagulation commencing along a guidewire surface. Additionally, precise directional control in laser angioplasty is of the utmost importance to assure accurate aiming of the laser beam to ablate the attendant plaque. However, the only prior art catheters having multi-directional steerability are typically greatly in excess of practical angioplasty catheter diameters.
Thus, there remains a need for a small diameter steering device, which may be readily adapted for use in the construction of either guidewires or catheters, and which is especially suited for procedures such as balloon or laser angioplasty. Preferably, the steering device is constructed in a manner which permits a diameter as small as that of existing dilatation catheters or guidewires used in angioplasty applications, yet is capable of complete deflective movement, throughout a full 360.degree. range of motion, without axial rotation.